Re: [PATCH v2] fpga: dfl: afu: convert get_user_pages() --> pin_user_pages()

From: John Hubbard
Date: Sat May 23 2020 - 17:33:15 EST


On 2020-05-23 13:57, Moritz Fischer wrote:
On Fri, May 22, 2020 at 06:52:34PM -0700, John Hubbard wrote:
On 2020-05-19 13:14, John Hubbard wrote:
This code was using get_user_pages_fast(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages_fast() + put_page() calls to
pin_user_pages_fast() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
https://lwn.net/Articles/807108/

Cc: Xu Yilun <yilun.xu@xxxxxxxxx>
Cc: Wu Hao <hao.wu@xxxxxxxxx>
Cc: Moritz Fischer <mdf@xxxxxxxxxx>
Cc: linux-fpga@xxxxxxxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>


Hi Moritz and FPGA developers,

Is this OK? And if so, is it going into your git tree? Or should I
send it up through a different tree? (I'm new to the FPGA development
model).

I can take it, sorry for sluggish response.


That's great news, thanks Moritz! Sorry to be pushy, just didn't want it
to get lost. :)

thanks,
--
John Hubbard
NVIDIA